1. Field
One or more embodiments of the present invention relate to a negative active material, a lithium battery including the negative active material, and a method of manufacturing the negative active material.
2. Description of the Related Art
Lithium secondary batteries used in portable electronic devices for information communication (such as personal digital assistants (PDAs), mobile phones, or notebook computers), electric bicycles, electric vehicles, or the like, have a discharge voltage that is at least twice as high as that of a comparable (conventional) battery, and thus, have a high energy density.
Lithium secondary batteries generate electric energy by oxidation and reduction reactions occurred when lithium ions are intercalated/deintercalated into/from a positive electrode and a negative electrode (each including an active material that enables intercalation and deintercalation of lithium ions), with an organic electrolytic solution or a polymer electrolytic solution interposed between the positive and negative electrodes.
Research is being conducted about various forms of carbonaceous materials (such as synthetic and natural graphite, or hard carbon), which are capable of intercalation/deintercalation of lithium, and non-carbonaceous materials such as Si.
When a negative electrode material of a lithium secondary battery directly contacts an electrolyte, the electrolyte may undergo reductive cleavage at a low electric potential. Accordingly, during a charging process of lithium, reactivity between the negative electrode material and the electrolyte of the lithium secondary battery may increase to form a thin film on a surface of the negative electrode. Here, the higher the temperature of the reaction in the battery, the greater the reactivity between the negative electrode material and the electrolyte. Due to the thin film, lithium ions and electrons are consumed, thereby deteriorating lifespan characteristics of the lithium secondary battery. Also, the film undergoes exothermal decomposition reaction at a high temperature of about 100° C. or greater, and as the amount of the film increases, the amount of heating increases, which may deteriorate the high temperature stability of a cell. Due to this phenomenon, high temperature stability and lifespan characteristics of a lithium secondary battery may deteriorate.
Accordingly, development of a negative active material having improved high temperature stability and lifespan characteristics is needed.